1. Field of the Invention
The present invention relates generally to time setting devices, and more particularly to rotatable encoders. Such devices are used to convert a dial rotation to a digital representation for use with digital circuitry.
2. Description of the Prior Art
In electronic time pieces and timers, mechanical and electrical time selection and setting systems have been proposed. One of such systems is represented by U.S. Pat. No. 4,336,609 wherein a piezoelectric arm is flexed by a rotating element to develop pulses relating to the rotation. A discriminating circuit is used to determine which direction the rotation occurred. Another version is presented in U.S. Pat. No. 4,449,832 in which a rotary dial controls a disk having spaced slits. An opto-electronic device detects the passage of the slits to generate the data, but rotation direction is not detected. In U.S. Pat. No. 4,4198,018 there is presented an electro-mechanical device which operates switches in response to dial rotation. This device discriminates between direction of rotation by use of phase differences between two generated pulse trains. A winding stem is fitted with two cams, each cam being phase displaced with respect to the other. These cams operate to contact and flex resilient electrically conductive members to thereby produce phase shifted pulse trains.